1. Technical Field
The present invention relates to a transmitter, a receiver, a mobile communication system and a synchronization channel transmission method.
2. Background Art
In multi carrier transmission schemes such as multi carrier CDMA (Multi Carrier Code Division Multiple Access: MC-CDMA) scheme and OFDM (Orthogonal Frequency Division Multiplexing) modulation scheme, an information signal is modulated with multiple subcarriers at the transmitter side, and a guard interval is inserted into a transmitted signal in order to reduce waveform distortion caused by multipath delayed wave.
As one method of detecting FFT (Fast Fourier Transform) timing in the multi carrier transmission scheme utilizing the OFDM modulation scheme, a method of detecting FFT timing by correlating a guard interval part inserted for each symbol is known. Also, a method of detecting FFT timing by transmitting the same signal as a timing detection signal twice repeatedly and correlating two symbols at the receiver side is known.
Meanwhile, a transmitter for multiplexing and transmitting a synchronization signal at certain timing is known. (For example, see patent document 1.) In this transmitter, the synchronization signal is transmitted throughout all subcarriers in a burst manner. In the transmitter, for example, if start time of a single scramble code pattern is synchronized with transmitting timing of the synchronization signal, the synchronization signal might be transmitted twice during a repetition interval .tau. of the single scramble code pattern.
Patent document 1: Japan Laid Open Patent Application No. 2003-152681
Non-patent document 1: R. L. Frank and S. A. Zadoff, “Phase shift pulse codes with good periodic correlation properties”, IRE Trans. Inform. Theory, vol. IT-B, pp. 381-382, 1962
Non-patent document 2: D. C. Chu, “Polyphase codes with good periodic correlation properties”, IEEE Trans. Inform. Theory, vol. IT-18, pp. 531-532, July 1972
Non-patent document 3: A. Milewski, “Periodic sequences with optimal properties for channel estimation and fast start-up equalization”, IBMJ. Res. Develop., vol. 27, No. 5, pp. 426-431, 1983
Non-patent document 4: B. M. Popovic, “Generalized chirp-like polyphase sequence with optimum correlation properties”, IEEE Trans. Inform. Theory, vol. 38, pp. 1406-1409, July 1992
Non-patent document 5: N. Suchiro and M. Hatori, “Modulatable orthogonal sequences and their application to SSMA systems”, IEEE Trans. Inform. Theory, vol. 34, pp. 93-100, January 1998
Non-patent document 6: 3GPP TS25.213 Spreading and modulation (FDD)